Startup sequence doesn't work (very irregular)

When I try to start my headphones, the power indicator just flashes very briefly and dimly. The NC activates for a little bit, but the startup sound doesn't play, and the NC sometimes shuts down again. When I toggle the power to the off position, the light flashes more brightly, and the bluetooth connection and shutdown sounds are played before turning off.

If I hold down the power switch when starting, it sometimes makes the indicator light stay on, and very occasionally do the headphones boot up (maybe every 20 tries or so), but sometimes they stop working again immediately.

See this video for an example: https://www.youtube.com/watch?v=YzvnaKmj...

I opened them up and checked for anything off, but I can't see any corrosion or any loose cables/connectors.